Why do wind turbine transformers fail so often?
June 9, 2010 by KRemington
Filed under Wind Power News
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2 Comments
Tom Steeber, Vice President, Pacific Crest Transformers, Medford, Oregon, pacificcresttrans.com
Using conventional off-the-shelf distribution transformers to cut costs is downright foolish. The unusual duty cycle of wind energy calls for an updated design.
A rush to install wind turbines has outstripped the usual developmental learning curve, one in which new technologies mature by trial and error, and define equipment that is well suited for the job at hand. In this 21st century land rush to cash-in on wind energy, developers are often trading low initial costs for higher total costs of ownership which is eventually shouldered by wind farm owners and operators. Nowhere is this more evident than with wind-turbine generator (WTG) step-up transformers.
The WTSU model step-up transformer from Pacific Crest Transformers, intended for duty on wind farms, features round coils, a cruciform, mitered core with heavy-duty clamping and a proprietary pressure-plate design, as well as a premium no-load tap changer. Coil-end blocking with heavy duty 3 gauge steel bracing and proprietary pressure plates contains axial forces exerted during a fault condition. These forces can cause telescoping of the coils, shortening transformer life. A cooling system shortens the path that heat generated within core and coils must take to reach the cooling fluid.
These devices take the approximately 460 V from the generator and step it up to about 34.5 kV. Then a collector on the wind farm further steps the synchronized power from a group of turbines to that of the grid, often 138 kV or more.
Historically the WTG transformer function has been handled by conventional, off-the-shelf distribution transformers. But a relatively large number of recent failures has convinced many that WTG transformer designs must be substantially more durable.
In fact, using conventional off-the-shelf distribution transformers as a low cost solution is folly. Some site operators keep spare transformers at their wind farms to fix the frequent outages caused by standard distribution transformers used where they do not belong. That is a waste of capit